One looked like a dinosaur(could be, i mean, preds have been hunting for a while). I think I recognized one from star wars. I'm quite sure preds are not limited to humans and aliens to hunt.
The larger one was probably the skull of a gro'ty (or however you spell that thing's name) but we don't know for sure because they haven't discussed it, the skulls they wanted us to pay attention to were the human ones and the single Xeno skull.